docs: def pretty_const(self, index):
          """
          a tuple of the pretty type and val, or (None, None) for invalid
          indexes (such as the second part of a long or double value)
          """
  
          t, v = self.consts[index]
          if not t:
              return None, None
          else:
              return _pretty_const_type_val(t, v)